1. Field of Invention
This invention relates generally to electrical interconnection systems and more specifically to electrical interconnection systems, such as high speed electrical connectors, with improved signal integrity.
2. Discussion of Related Art
Electrical connectors are used in many electronic systems. Electrical connectors are often used to make connections between printed circuit boards (“PCBs”) that allow separate PCBs to be easily assembled or removed from an electronic system. Assembling an electronic system on several PCBs that are then connected to one another by electrical connectors is generally easier and more cost effective than manufacturing the entire system on a single PCB.
Electronic systems have generally become smaller, faster and functionally more complex. These changes mean that the number of circuits in a given area of an electronic system, along with the frequencies at which those circuits operate, have increased significantly in recent years. Current systems pass more data between PCBs than systems of even a few years ago, requiring higher density electrical connectors that operate at higher frequencies.
As connector density signal frequencies increase, there is a greater possibility of electrical noise being generated in the connector as a result of reflections caused by impedance mismatch or cross-talk between signal conductors. Therefore, electrical connectors are designed to control cross-talk between different signal paths and to control the impedance of each signal path. Shield members, which are typically metal strips or metal plates connected to ground, can influence both cross-talk and impedance when placed adjacent the signal conductors. Shield members with an appropriate design can significantly improve the performance of a connector.
Different shielding arrangements are more or less effective, depending on the overall construction of the connector. For example, electrical connectors can be designed for single-ended signals or differential signals. A single-ended signal is carried on a single signal conducting path, with the voltage relative to a common reference conductor being the signal. Differential signals are signals represented by a pair of conducting paths, called a “differential pair.” The voltage difference between the conductive paths represents the signal. In general, the two conducing paths of a differential pair are arranged to run near each other. No shielding is desired between the conducting paths of the pair, but shielding may reduce cross-talk when used between differential pairs.
Despite recent improvements in high frequency performance of electrical connectors provided by shielded electrical connectors, it would be desirable to have an interconnection system with even further improved performance.